Source Glycolysis (EMP) Transition reaction Krebs cycle Total: Carbon Flow Molecules of Reduced Coenzymes Produced Net ATP Molecules Made by Substrate- Level Phosphory- lation Net ATP Molecules Made by Oxidative Phosphory- lation Theoretical Maximum Yield of ATP Molecules Substrate-level phosphorylation during glycolysis and the citric acid cycle accounts for four ATP. Oxidative phosphorylation accounts for 32 or 34 ATP, and the grand total of ATP is therefore 30-32ATP. Cells differ as to the delivery of the electrons from NADH generated outside the mitochondria. If they are delivered by a shuttle mechanism to the start of the electron transport system, 6 ATP result; otherwise, 4 ATP result. 2.5 ATP per NADH and 1.5 per FADH?. Further, the transfer of 2 e-from NADH to O2 results in 10 protons being pumped. 7-43